2003 2.0 HDI Poor fuel consumption

[Norfolkboy]

Only getting 33 mpg out of this car, driven on the same routes and in the same style (or lack of it), my previous 1.9 DW8 was getting 45 mpg.  No smoke, no apparent leaks.  Car appears hesitant at low revs/higher gears, certainly doesn't pull as well at low revs as the 1.9.  Occaisional very brief cut out or misfire at steady speeds.  Ideas please.

[jj9]

If you haven't already I would check the obvious first,

Are the brakes free and not binding slightly, feel the steel / alloy of the wheels after a run are they all the same temperature.
Is the Air filter clean and in good condition.
When was the fuel filter last changed.
Check that all the air pipework from the air filter to the inter cooler to the turbo is in place and secure.
Can you hear the turbo working.

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[Norfolkboy]

If you haven't already I would check the obvious first,

Are the brakes free and not binding slightly, feel the steel / alloy of the wheels after a run are they all the same temperature.
Is the Air filter clean and in good condition.
When was the fuel filter last changed.
Check that all the air pipework from the air filter to the inter cooler to the turbo is in place and secure.
Can you hear the turbo working.

.

Thanks for the response.  Brakes are free, air filter good, fuel filter and housing recently changed due to inlet air leak.  Hoses look OK but will look again.  No idea what to listen for on the turbo, this is my first turbo diesel.

[jj9]

I've never had a 2.0 HDI but I know a few on the forum do have them or have had them and they should be a lot better on the fuel & performance than yours.

You should be able to hear a slight turbo whistle when you rev the engine, however that said you can't always make it out.

If you follow the air intake pipework it should go to the Air filter then to the turbo, it will then come out and go to the intercooler at the front of the car, then to the inlet manifold, check that there are no splits or leaks in the pipework.

The turbo is at the back of the engine, there will be a small diameter vacuum pipe going to the diaphragm on it, follow this pipework around the engine bay and make sure it's all connected and doesn't have any splits.

I think the MAF meter (Mass Air Flow) can be a problem on this engine, I think if you unplug it and try driving if it is at fault the performance should be better.

Cancunia had the 2.0 HDi so he knows his way around them, he might be able to give some better pointers regarding the MAF & turbo.


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[polar]

I would go for the MAF, the 2.0 are not brilliant on fuel but you should be getting about 40mpg.

Have you done a diag to make sure the temperature sender is reading something close to what it should be?

The temperature senders can read way off and cause excessive fuel consumption.

[cancunia]

Yeah, as above, from the description about lack of power, I'd say unplug the MAF & see if it goes better. Mine was getting about 42MPG according to the trip computer with or without the MAF.
You may well get the EML on without the MAF, but you can ignore that until the MOT if you like so long as that's all there is putting the EML on.
Also, if you don't already have one, get a code reader and see what comes up. A faulty MAF will probably give you an EGR related fault while it's plugged in.

[Norfolkboy]

Thanks for all responses,   I disconnected the MAF and performance improved.  As an Engineer, I just had to investigate  the function of the MAF and the symptons of its failure.  A good match to my problems, including a tendency to die shortly after start (I thought it was just me stalling an unfamiliar car).  Just been out to buy a can of MAF cleaner, will let you know how it goes.  Intrigued by the temp sensor suggestion, the car is very slow to warm up despite a new thermostat.  Heater output seems to match the guage reading.  Might try masking part of the rad in the current weather.

[cancunia]

Glad to see that you've had some improvement. Did the EML come on?
I bought a MAF for about £25 on ebay, it came with a 1 year warranty but I sold the car after a few weeks so don't know how well it's lasted. A supplier that has a good rep is ukdieselparts, might be worth giving them a look.
The 2.0 will take a while to warm up.

[Norfolkboy]

EML showed as normal, pretest worked, went out on start. Revs steady at 950 immediately as opposed to seeing rev drops previously. Looks as though it could be a winner. Thanks for the link.

[cancunia]

EML showed as normal, pretest worked, went out on start. Revs steady at 950 immediately as opposed to seeing rev drops previously. Looks as though it could be a winner. Thanks for the link.

Interesting! Some ECU firmware lights the EML, some not. It's the same with the EGR from what I've read. Without the MAF, the ECU apparently uses a static standby fuel map, as opposed to a dynamic map based on airflow. The only difference I noticed with a new MAF (apart from the EML) was a lack of judder at around 40mph in 4th & 50 in 5th.

I now have a 1.6HDi which, according to the MOT history had the EML on for about 6 years. It was the MAF causing it, I had to put a new MAF on for the MOT, can't say that I've noticed any real difference in performance.